Jaimie,
Most likely it would be better and much more kind to lie to you. But your should resign yourself to the facts that you will never ever be finished buying tooling for a mill. A lathe is slightly better though. How much is your budget, and how much electrical power and room do you have?
Your mill is a fairly decent machine to start out with, and far larger than my first mill was. Motorcycle work? Leaving aside anything like engine work and cylinder reboreing etc. Then your wanting to do mostly parts replacement and that customisation, and then maybe building up to parts such as disc brakes for diameter. Single phase motors on machine tools are ok, but a real upgrade later on is using proper 3 phase equipment.. VFD's today make this more than within reach and very much worthwhile.
FWIW, your current mill probably won't be something you stick with, but it's a great learning tool, with some luck it's also a common taper like a R8 so the tooling can be transfered to a larger mill when you do upgrade. Your lathe will be exactly the same idea. You will if you stick with this upgrade to larger equipment in the future. Everyone does. So for right now if you want to buy new? I'd suggest something like a 280 V-F. It's rebadged by numerous dealers and is possibly built by Weiss In Nanjing China. There's obviously far better and larger, but this would be a good learning tool. Given some experience and knowledge, then you might then start looking at the better quality used industrial machines. That does require that experience and knowledge before you can even judge exactly what you need or want. But most tooling you'd tend to buy for something like that 280 would be useable on another machine. Tailstock tooling and the smaller MT tapers wouldn't transfer though.
But the very best advise I can offer is if you think you'll stick with machining as a hobby for even the next 10 years? Then please save your money and buy the very best industrial grade cutting tools and measuring equipment you can afford. In the long run it's the cheapest bang for the buck. There is no such thing as good cheap durable cutting tools. The much more expensive industrial tooling cut's, performs and last's far beyond the extra expense involved. And if you were to add the word accuracy, then the same can be said about metrology equipment.Think about it,if you can't measure it dependably and repeatably, then you can't build it to the required accuracy. I tried the cheap cutting tools and measuring equipment, I can't afford to buy it anymore.
Pete